I really like both cities, how long would you be going for?
Seville - gorgeous architecture, good value for money, top notch food at reasonable prices, buzzy atmosphere, interesting history with the palace and the cathedral, some fantastic hotels for decent prices. Can easily do a day trip to Jerez or Cádiz.
Cons - can be very busy with tourists (probably not a concern in February), flight choices can be fewer, on local holidays it can be very busy and difficult on transport, there can be a pickpocketing problem, it’s a horrible city to drive in, it’s a bit more necessary to have some Spanish to get by in the less touristy bits.
Malaga - beaches right in the city, good museums and art galleries, Roman history, nice bars, good food (especially fish / seafood), usually lots of choice of flights from many airports, usually fewer tourists in the actual city itself.
Cons - not so good value for money for hotels or food, less to do and see than many of the big Spanish cities so not great for more than a couple of days of sightseeing, the beaches are nice and perfectly pleasant but not stunningly so, if that makes any sense, it can be very windy and therefore quite chilly in the Winter.